package redblack;

import map.Map;

/**
 * 红黑树
 *
 * @author: yxyi
 * @mail: yxyi@iflytek.com
 * @date: 2019-01-12
 */
public class RBTree<K extends Comparable<K>, V> implements Map<K, V> {

    private static final boolean RED = true;
    private static final boolean BLACK = false;

    private class Node {
        public K key;
        public V value;
        public Node left, right;
        public boolean color;

        public Node(K key, V value) {
            this.key = key;
            this.value = value;
            this.color = RED;
        }
    }

    private Node root;
    private int size;

    public RBTree() {
    }

    private boolean isRed(Node node) {
        if (node == null) {
            return BLACK;
        }
        return node.color;
    }

    /**
     *  node                 x
     *  / \       左旋转     /  \
     * T1  x     -------> node T3
     *    / \             / \
     *   T2 T3           T1 T2
     *
     * @param node
     * @return
     */
    private Node leftRotate(Node node) {
        Node x = node.right;

        node.right = x.left;
        x.left = node;

        x.color = node.color;
        node.color = RED;

        return node;
    }

    /**
     *      node               x
     *     /   \    右旋转    /   \
     *    x    T2  -------> z    node
     *   / \                     / \
     *  z  T1                   T1 T2
     *
     * @param node
     * @return
     */
    private Node rightRotate(Node node) {
        Node x = node.left;

        node.left = x.right;
        x.right = node;

        x.color = node.color;
        node.color = RED;

        return node;
    }

    // 颜色翻转
    private void flipColors(Node node) {
        node.color = RED;
        node.left.color = BLACK;
        node.right.color = BLACK;
    }

    @Override
    public void add(K key, V value) {
        root = add(root, key, value);
        // 保持根节点是黑色的
        root.color = BLACK;
    }

    private Node add(Node node, K key, V value) {
        if (node == null) {
            size++;
            return new Node(key, value);
        }

        if (node.key.compareTo(key) < 0) {
            node.left = add(node.left, key, value);
        } else if (node.key.compareTo(key) > 0) {
            node.right = add(node.right, key, value);
        } else {
            node.value = value;
        }

        // 左旋转
        if (isRed(node.right) && !isRed(node.left)) {
            node = leftRotate(node);
        }
        // 右旋转
        if (isRed(node.left) && isRed(node.left.left)) {
            node = rightRotate(node);
        }
        // 颜色翻转
        if (isRed(node.left) && isRed(node.right)) {
            flipColors(node);
        }

        return node;
    }

    @Override
    public V remove(K key) {
        Node node = getNode(root, key);
        if (node != null) {
            root = remove(root, key);
            return node.value;
        }
        return null;
    }

    @Override
    public boolean contains(K key) {
        return getNode(root, key) != null;
    }

    @Override
    public V get(K key) {
        Node node = getNode(root, key);
        return node == null ? null : node.value;
    }

    @Override
    public void set(K key, V value) {
        Node node = getNode(root, key);
        if (node == null) {
            throw new IllegalArgumentException(key + "doesn't exist!");
        }
        node.value = value;
    }

    @Override
    public boolean isEmpty() {
        return size == 0;
    }

    @Override
    public int getSize() {
        return size;
    }

    private Node getNode(Node node, K key) {
        if (node == null) {
            return null;
        }
        if (key.compareTo(node.key) == 0) {
            return node;
        } else if (key.compareTo(node.key) < 0) {
            return getNode(node.left, key);
        } else {
            return getNode(node.right, key);
        }
    }

    private Node remove(Node node, K key) {
        if (node == null) {
            return null;
        }
        if (node.key.compareTo(key) < 0) {
            node.left = remove(node.left, key);
            return node;
        }
        if (node.key.compareTo(key) > 0) {
            node.right = remove(node.right, key);
            return node;
        }
        if (node.left == null) {
            Node rightNode = node.right;
            node.right = null;
            size--;
            return rightNode;
        }
        if (node.right == null) {
            Node leftNode = node.left;
            node.left = null;
            size--;
            return leftNode;
        }
        Node successor = minimum(node.right);
        successor.left = node.left;
        successor.right = removeMin(node.right);

        node.left = node.right = null;

        return successor;
    }

    private Node removeMin(Node node) {
        if (node.left == null) {
            Node rightNode = node.right;
            node.right = null;
            size--;
            return rightNode;
        }

        node.left = removeMin(node.left);

        return node;
    }

    public Node minimum(Node node) {
        if (node.left == null) {
            return node;
        }
        return minimum(node.left);
    }
}
